Antihydrogen Electric Charge Neutrality: A New Limit from ALPHA at CERN

The equivalence of the absolute value of the electric charge of the electron and of the proton is experimentally well-established. It also finds strong theoretical motivations within the Standard Model. A similar measurement on positrons and antiprotons provides, in addition, a test of the CPT invariance. The ALPHA collaboration set a new upper limit on the electric charge $Qe$, where $e$ is the elementary charge, of the antihydrogen atom by applying stochastic acceleration to the magnetically confined antiatoms. The limit $|Q|<7.1\times10^{-10}$ (1$\sigma$ confidence level) is a 20-fold improvement on the previously best measurement. The present result places an improved limit on the positron charge anomaly of about 1 ppb.